Counting Down The Moons

Obviously, the Earth’s Moon is pretty great, as moons go. For the broad sweep of human history, this beacon of our night sky has inspired lovers and songwriters and literature, encouraged early humans to develop calendars and create the science of astronomy, influenced the tides of our oceans, and provided a bright light to help illuminate the dark night and early morning hours. For a dead, lifeless celestial body that is pockmarked with craters, that’s a pretty impressive list of achievements.

To the folks at Popular Mechanics, though, our Moon isn’t at the top of the lunar heap. When they decided to sit down and rank the more than 150 moons in the solar system — including ones you’ve probably never heard of, like Epithemius and Janus, which share the same orbit around Saturn, Dactyl, a moon that actually orbits an asteroid rather than a planet, and Mimas, which looks uncomfortably like the Death Star from Star Wars — our Moon didn’t fare very well. In fact, the Moon barely cracks the top ten, coming in at number 8. The Popular Mechanics crew concludes that it’s just not as interesting from a scientific standpoint, or as charismatic, as other moons. In fact, you get the sense from the comments reported in the article that the number 8 slot is actually kind of a pity ranking, given just because the Moon is our moon and we give it a capital M. The Old Man in the Moon has got to be disappointed.

The Moon came in behind Iapetus, Ganymede, Europa, Triton, Enceladus, Io, and the top-rated moon, Titan, which also orbits Saturn. These bodies all have features the Moon lacks, like liquid oceans, actual atmospheres made up of exotic combinations of chemicals, volcanic activity, bright colors, or the possibility of alien life.

OK, I get it: but has anyone ever actually written a song about Enceladus, or Titan?

Checking Out Saturn’s Geometric Weirdness

NASA’s Cassini spacecraft has taken its first plunge past Saturn, and the results are pretty amazing.  On its dive, Cassini goes from 45,000 miles from Saturn’s surface to as close as 4,200 miles from the spinning cloud cover, and it even threaded the needle by passing between the planet and its famous rings — where Cassini was hit by a few stray particles.

The brief video above shows some of the highlights of the first pass, and you can read about the first pass, and get links to the longer videos, here.  Forget the fact that the video footage from Cassini is black and white, and focus on the fact that we are seeing video taken from a planet that is more than 750 million miles away from our little part of the universe.  And take a good look at Saturn’s incredible strangeness — like the defined hexagonal shape that is formed by the cloud formations at Saturn’s north pole and the completely distinct eye that is found at the center of the polar vortex.  What could cause the clouds to form such unusual, seemingly unnatural shapes?

Why, aliens, of course.

The Warm Seas of Enceladus

It’s becoming increasingly clear that there is alien life out there, in our solar system and beyond.  To the extent that people still cling to the geocentric notion that Earth is the only planet in the universe capable of supporting life, it’s time to think again.

The latest indicator of that reality came yesterday, when NASA announced that its Cassini spacecraft had found promising signs that alien life may exist on Enceladus, one of the moons orbiting Saturn.  Cassini flew through a plume that was spraying out of the icy shell covering Enceladus and detected molecular hydrogen.  That’s a big deal because molecular hydrogen is created by interaction between warm water and rock, and along with carbon dioxide is the kind of food that early, microbial life forms can thrive on.  Scientists believe that life on Earth may have started in the same kind of environment surrounding the deep geothermal vents in our oceans — and if life started here, why shouldn’t it also occur in the same environment elsewhere?

Does that mean that there is, in fact, some form of life already existing on Enceladus?  Not necessarily, because the large amount of molecular hydrogen and carbon dioxide detected by the Cassini spacecraft suggests that there isn’t much, if any, bacteria or microbial life on Enceladus actually consuming the food — a fact that doesn’t surprise scientists, because they think Enceladus is relatively young and it takes a long time for life to emerge.

But equally intriguing is that NASA also announced that the Hubble telescope found evidence of similar plumes on Europa, a much older moon orbiting Jupiter.  Because Europa has apparently been around for billions of years longer than Enceladus, the combination of molecular hydrogen, carbon dioxide, and time might have allowed life to gain a foothold there.  It’s something we’re going to have to explore.

Into Saturn’s Rings

Yesterday, NASA’s Cassini spacecraft began the final stage of its mission — a series of maneuvers that will give the probe a close-up look at the rings of Saturn.

First launched in 1997, Cassini has been knocking around the outer reaches of the solar system for years, exploring Saturn and its moons, and it has made some interesting discoveries.  Cassini’s foray into Saturn’s rings will be its grand finale.  The spacecraft will dive into the gap between Saturn and its rings, loop around the planet’s poles, and take a closer look at Saturn’s idiosyncratic features and study the gas and dust particles that make up the rings.

The mission then will close with Cassini flying close to the planet’s surface and ultimately plummeting into Saturn’s atmosphere in a final suicidal act.  By then, Cassini will be out of fuel, and scientists don’t want to take the chance that the spacecraft could somehow crash into one of Saturn’s moons — moons that might be habitable — so Cassini will be intentionally steered into the planet to go out in a blaze of glory.

Saturn’s rings were first seen by humans in 1610, when Galileo Galilei turned his telescope to the night sky, and they have been the object of wonder and fascination ever since.  The final stages of Cassini’s two-decade mission will give us more information about the rings than we have ever had before.  And it may answer some nagging questions, like whether the rings are the same age as the planet itself, or were they formed later?  And are there small moons embedded in the rings that might explain their shape and configuration?

NASA’s unmanned space exploration program should be the source of pride to all Americans.  Through countless missions to the inner and out solar system, it has added exposed our planetary neighborhood as a constantly surprising place, with potential sources of water, rich mineral deposits, and places that might conceivably harbor other forms of life.  The Cassini mission is just the latest chapter in an ever-encouraging tale that shows that the human impulse to explore and discover still runs strong.

The Real-Life Death Star

Saturn has 62 moons.  One of them, called Mimas, looks familiar to anyone who’s ever watched the original Star Wars:  it’s a dead ringer for the Death Star.

Mimas is weird in other ways, too.  It’s the smallest round moon ever discovered.  It has an apparent impact crater so large that it looks like it should have shattered the moon into tiny pieces.  And Mimas accountably wobbles, too.  In fact, it wobbles so dramatically that scientists are stumped about how the pronounced wobble could possibly be caused.  The competing theories range from some large stone under the surface of the impact crater, to a core that is unaccountable shaped like a rugby ball, to an underground ocean that is sloshing back and forth even though Mimas is so cold that it’s hard to see how liquid water can exist.  And so, the scientists argue.

Let’s see — the smallest round moon known to anyone that looks exactly like the Death Star.  Isn’t the real answer obvious?  Help us, Obi-Wan Kenobi!  You’re our only hope!

 

Discovering A Salt Water Moon

America’s unmanned space probes continue to do amazing things — including discovering that one of Saturn’s moon has salt water oceans like those on Earth.

The discovery was made by the Cassini spacecraft, which has been flying around the huge gas giant and its famous rings.  Cassini reached a point within 46 miles of the south pole of ice-covered Enceladus, one of Saturn’s many moons, and on its close pass Cassini actually flew through the jets of water vapor and ice that make up the geysers emanating from the moon.  In so doing, the probe “tasted” the vapor and determined that it consists of water, organic compounds, and salt, at the same salinity levels as Earth’s oceans.

The evidence suggests that there are liquid oceans underneath Enceladus’ icy crust, and that the water may be in contact with the moon’s rocky core — which could be supplying the chemical compounds that are the building blocks of life.  This discovery makes Enceladus a prime candidate for another mission designed to determine whether life in some form actually exists on the moon.  We’ll just have to hope that we can find the money necessary to fund the mission that will follow up on this very intriguing discovery.

 

Sowing Earthlife

Those who are intrigued by the possibility of extraterrestrial life may be interested in a study that indicates that Earth itself could have been the source of life on other planets and moons in our solar system.

The study looked at the dispersion of debris from asteroid impacts on the Earth’s surface.  It found that such debris is far more likely to reach Mars, or even Jupiter and Saturn and their moons, than was previously thought.  If such debris contained small life forms, they therefore could have reached other places that are capable of sustaining life.  Of course, any microbes and other organisms on the debris would have to be hardy enough to survive years of travel through space, exposure to radiation, the fall to the surface of another planet, and the different atmospheres and living conditions on those planets — but we know that there are organisms that can survive such conditions, and we also know that life is tenacious and is found in even the most hostile and extreme climates on Earth.

We won’t know, of course, whether this scenario could actually have produced life elsewhere until we find such life and test it.  If we do find such life, however, it will give new meaning to the phrase “Mother Earth.”

 

Titanic Indications of Extraterrestrial Life

The Daily Mail has an interesting piece today on tantalizing indications that there might be a form of life on Titan, a moon that orbits Saturn.  Titan is one of the largest moons in the solar system and has a dense atmosphere.

The Daily Mail piece reports on two articles recently published in scientific journals that attempt to find evidence of life by focusing on the presence and absence of certain elements and chemicals.  One article notes that hydrogen that is found in Titan’s atmosphere seems to disappear when it reaches the surface and posits that a potential explanation is that the hydrogen is breathed, or otherwise consumed, by life forms on the surface.  The second article suggests that a similar conclusion could be inferred from the absence of still another chemical on the surface.

It is always risky to make broad extrapolations based on the absence of something, but the scholarly articles and the indicators they highlight are intriguing.  They confirm, once again, that exploring the moons of Saturn and Jupiter could be tremendously rewarding from a scientific standpoint.  If there is life on Titan, however, it would be quite different from life on Earth.  Although there is liquid on Titan, the liquid is methane, and scientists think life would be methane-based.

Cool Stuff From Cassini

NASA’s Cassini space probe flew by the Saturn moon Enceladus and sent back some pretty cool images.  Enceladus is one of Saturn’s 61 moons — 23 if you count only those that have regular orbits — and is pretty interesting.  It is the sixth largest moon of Saturn, and its fissured, ice-covered surface spews vast plumes of water vapor into space.  The NASA website has some interesting pictures.

Enceladus, for those who don’t have an encyclopedic recollection of Greek mythology, was one of the Giants who was defeated by the Olympian Gods.